In human anatomy, the pleural cavity is the body cavity that contains the lungs. The lungs are surrounded by the pleurae, a serous membrane which folds back upon itself to form a two-layered, membrane structure. The thin space between the two pleural layers is known as the pleural space; it normally contains a small amount of pleural fluid. The outer pleura (parietal pleura) is attached to the chest wall. The inner pleura (visceral pleura) covers the lungs and adjoining structures, i.e. blood vessels, bronchi and nerves.
The parietal pleura is highly sensitive to pain; the visceral pleura is not due to its lack of sensory innervation.
In normal pleurae, most fluid is produced by the parietal circulation (intercostal arteries) via bulk flow and reabsorbed by the lymphatic system. Thus, pleural fluid is continuously produced and reabsorbed. The rate of reabsorption may increase up to 40x before significant amounts of fluid accumulate within the pleural space.
In humans, there is no anatomical connection between the left and right pleural cavities, so in cases of pneumothorax, the other hemithorax will still function normally.